1. Field of the Invention.
The present invention, generally, relates to hydraulic brake mechanisms and, more particularly, to mechanisms used to retract an actuating piston contained within a hydraulic disk brake mechanism.
Hydraulic disk brake mechanisms are found in use throughout the world today. While hydraulic disk brakes have many advantages over drum type brakes, they are far from consistent in operation.
Often when pressure is removed from the brake pedal, the actuating piston fails to retract sufficiently which, as a result, maintains the brake pad in contact with the rotor disk. This residual contact creates friction, causing an increase in temperature to occur.
The increase in temperature lead to a decrease in braking ability, a phenomenon known as fading. The residual friction also serves to accelerate brake pad wear and increases vehicular fuel consumption.
2. Description of Prior Art
Magnetic releases for friction brakes are already known. For example, U.S. Pat. No. 3,470,987 to Kroeger, that issued Oct. 7, 1969, describes the use of a multiple disk friction brake mechanism, mounted on the end bell of an electric motor. The force exerted by brake applying springs is overcome by energizing a winding.
A device disclosed in U.S. Pat. No. 3,221,845 to Hansen, that issued Dec. 7, 1965, also relies upon a spring actuated braking mechanism for an electric motor. An electromagnet is used to counteract the force of the springs, thereby removing the braking force.
U.S. Pat. No. 4,820,946 to Gutbrod, that issued Apr. 11, 1989, describes an adjustable electromagnetic brake mechanism in which a brake spring applies compressive force to an armature plate and friction discs to apply a braking force. An electrical coil creates an electromagnetic force on an armature plate in a direction to release the brake.
U.S. Pat. No. 4,623,044 to Ohta et al, that issued Nov. 18, 1986, describes a brake mechanism utilizing the change in dimension of a piezoelectric member, when a voltage is applied, to develop additional braking force, rather than to withdraw braking force.
U.S. Pat. No. 4,605,104 to Thompson, that issued Aug. 12, 1986, describes an actuating mechanism that relies upon elastic properties, rather than magnetic, to assist in the retraction of the brake actuator.
U.S. Pat. No. 4,662,483 to Boeck, that issued May 5, 1987, describes a disc brake retractor mechanism with compression springs to assist in the retraction of the braking apparatus.
U.S. Pat. No. 4,629,039 to Imoto et al, that issued Dec. 16, 1986 describes an alternate braking apparatus using a piezoelectric device.
U.S. Pat. No. 4,067,420 to Fabris, that issued Jan. 10, 1978, describes a disc brake mechanism with an electromagnetic release mechanism.
While the structural arrangements of these prior art devices at first appearance have similarities with the device of the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.